Chapter 9 Carbonation of steel slag

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Book Chapter

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Sustainable Utilization of Carbon Dioxide in Waste Management

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In this chapter, we discussed the sources and chemical and mineralogical characteristics of a variety of steel and iron slags, such as basic oxygen furnace (BOF), electric-arc furnace (EAF), ladle furnace (LF), blast furnace slag (BFS), and argon oxygen decarburization (AOD) slag. Also, we discussed the current utilization of steel and iron slags in civil engineering applications, such as cement production, concrete aggregate, asphalt aggregate, road bases, and subbases, and soil stabilization, as well as other miscellaneous applications, such as steelmaking, fertilizer production, linings for waterways, daily landfill covers, railroad ballast, and waste management. Problems associated with such utilization were highlighted and discussed and mitigation measures were provided. Slag pretreatment such as hydration was discussed with emphasis on the newly formed products that might hinder the hydration process. Also, mitigation methods were highlighted. Carbonation methods, such as gas-solid versus gas-aqueous media solid, direct (or single-step) versus indirect (or multi-step), additive-enhanced or without chemical additives, and combination of the above processes, were discussed with specific case studies from the literature. For direct carbonation, we discussed a variety of carbonation methods such as (a) fluidized bed reactor; (b) high gravity rotating packed bed; (c) ultrasound; (d) spouted bed reactor; and (e) static packed bed with two moisture conditions (i) thin-film carbonation; and (ii) slurry carbonation. For indirect carbonation, a rotating packed bed, as an example, was used. For both direct and indirect carbonation, we discussed the effect of various controlling parameters on carbon uptake, such as gas pressure, temperature, concentration, flow rate, solid product layer characteristics, mass transfer coefficients, activation energy, the ratio of mineral-to-gas, ratio of available reacting species (Ca/Mg; Ca/Si, etc.), the concentration of reacting species, solution pH, solid-to-liquid ratio, humidity, nature of the bed reactor (static, rotating, fluidized, etc.), and reacting bed boundary conditions (open vs. closed). It was challenging to compare carbonation methods because they were done with different slags and operating conditions. However, dynamic systems such as fluidized bed, rotating bed, and ultrasonic would result in more carbon uptake than static bed due to their abilities to create an excellent hydrodynamic design within the vessel, increase the mass transfer rate, increase attrition rate, enhance the breaking up of the aggregated particles, continual detachment of the product layer and exposure of the unreacted core to further chemical reactions with carbonic species.





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Environmental Engineering | Environmental Sciences


Carbon sequestration, Carbonated slag utilization, CO2 sequestration, Fluidized bed reactor, High gravity rotating packed bed, Mineral carbonation, Reaction mechanisms, Reactor technologies, Slag pretreatment, Slurry carbonation, Spouted bed reactor, Static packed bed reactor, Steelslag, Thin-film carbonation, Ultrasound

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Open Access